Optical imaging system, image capturing unit and electronic device

ABSTRACT

An optical imaging system includes four lens elements which are, in order from an object side to an image side: a first lens element, a second lens element, a third lens element and a fourth lens element. Each of the four lens elements of the optical imaging system has an object-side surface facing toward the object side and an image-side surface facing toward the image side. The object-side surface of the first lens element is concave in a paraxial region thereof and has at least one convex shape in an off-axis region thereof. The object-side surface of the first lens element is aspheric. The image-side surface of the fourth lens element is concave in a paraxial region thereof. The optical imaging system has a total of four lens elements.

RELATED APPLICATIONS

This application claims priority to Taiwan Application 108110521, filedon Mar. 26, 2019, which is incorporated by reference herein in itsentirety.

BACKGROUND Technical Field

The present disclosure relates to an optical imaging system, an imagecapturing unit and an electronic device, more particularly to an opticalimaging system and an image capturing unit applicable to an electronicdevice.

Description of Related Art

With the development of semiconductor manufacturing technology, theperformance of image sensors has been improved, and the pixel sizethereof has been scaled down. Therefore, featuring high image qualitybecomes one of the indispensable features of an optical system nowadays.

Furthermore, due to the rapid changes in technology, electronic devicesequipped with optical systems are trending towards multi-functionalityfor various applications, and therefore the functionality requirementsfor the optical systems have been increasing. However, it is difficultfor a conventional optical system to obtain a balance among therequirements such as high image quality, low sensitivity, a properaperture size, miniaturization and a desirable field of view.

SUMMARY

According to one aspect of the present disclosure, an optical imagingsystem includes four lens elements. The four lens elements are, in orderfrom an object side to an image side, a first lens element, a secondlens element, a third lens element and a fourth lens element. Each ofthe four lens elements has an object-side surface facing toward theobject side and an image-side surface facing toward the image side.

The object-side surface of the first lens element is concave in aparaxial region thereof and has at least one convex shape in an off-axisregion thereof, and the object-side surface of the first lens element isaspheric. The image-side surface of the fourth lens element is concavein a paraxial region thereof. The optical imaging system has a total offour lens elements.

When an axial distance between the object-side surface of the first lenselement and an image surface is TL, a focal length of the opticalimaging system is f, a focal length of the second lens element is f2, anaxial distance between the first lens element and the second lenselement is T12, an axial distance between the second lens element andthe third lens element is T23, an axial distance between the third lenselement and the fourth lens element is T34, and a maximum image heightof the optical imaging system is ImgH, the following conditions aresatisfied:3.0<TL/f<6.0;T23<T12;T34<T12;−3.0<f/f2<0.40; and1.50<TL/ImgH<4.20.

According to another aspect of the present disclosure, an opticalimaging system includes four lens elements. The four lens elements are,in order from an object side to an image side, a first lens element, asecond lens element, a third lens element and a fourth lens element.Each of the four lens elements has an object-side surface facing towardthe object side and an image-side surface facing toward the image side.

The object-side surface of the first lens element is concave in aparaxial region thereof and has at least one convex shape in an off-axisregion thereof, and the object-side surface of the first lens element isaspheric. The object-side surface of the third lens element is convex ina paraxial region thereof. The image-side surface of the fourth lenselement is concave in a paraxial region thereof. The optical imagingsystem has a total of four lens elements, and the optical imaging systemfurther includes an aperture stop.

When an axial distance between the object-side surface of the first lenselement and an image surface is TL, a focal length of the opticalimaging system is f, an axial distance between the first lens elementand the second lens element is T12, an axial distance between the secondlens element and the third lens element is T23, an axial distancebetween the third lens element and the fourth lens element is T34, anaxial distance between the aperture stop and the image-side surface ofthe fourth lens element is SD, and an axial distance between theobject-side surface of the first lens element and the image-side surfaceof the fourth lens element is TD, the following conditions aresatisfied:3.0<TL/f<6.0;T23<T12;T34<T12; and0.34<SD/TD<1.20.

According to another aspect of the present disclosure, an imagecapturing unit includes one of the aforementioned optical imagingsystems and an image sensor, wherein the image sensor is disposed on theimage surface of the optical imaging system.

According to another aspect of the present disclosure, an electronicdevice includes the aforementioned image capturing unit.

According to another aspect of the present disclosure, an opticalimaging system includes four lens elements. The four lens elements are,in order from an object side to an image side, a first lens element, asecond lens element, a third lens element and a fourth lens element.Each of the four lens elements has an object-side surface facing towardthe object side and an image-side surface facing toward the image side.

The object-side surface of the first lens element is concave in aparaxial region thereof. The image-side surface of the second lenselement is concave in a paraxial region thereof. The image-side surfaceof the fourth lens element is concave in a paraxial region thereof. Theoptical imaging system has a total of four lens elements, and theoptical imaging system further includes an aperture stop.

When an axial distance between the object-side surface of the first lenselement and an image surface is TL, a focal length of the opticalimaging system is f, a focal length of the fourth lens element is f4, anaxial distance between the aperture stop and the image-side surface ofthe fourth lens element is SD, an axial distance between the object-sidesurface of the first lens element and the image-side surface of thefourth lens element is TD, a curvature radius of the object-side surfaceof the first lens element is R1, and a curvature radius of theimage-side surface of the first lens element is R2, the followingconditions are satisfied:3.0<TL/f<10.0;0.34<SD/TD<1.20;(R1+R2)/(R1−R2)<0.90; and−3.0<f/f4<−0.55.

According to another aspect of the present disclosure, an opticalimaging system includes four lens elements. The four lens elements are,in order from an object side to an image side, a first lens element, asecond lens element, a third lens element and a fourth lens element.Each of the four lens elements has an object-side surface facing towardthe object side and an image-side surface facing toward the image side.

The object-side surface of the first lens element is concave in aparaxial region thereof and has at least one convex shape in an off-axisregion thereof, and the object-side surface of the first lens element isaspheric. The object-side surface of the third lens element is convex ina paraxial region thereof. The optical imaging system has a total offour lens elements.

When an axial distance between the object-side surface of the first lenselement and an image surface is TL, a focal length of the opticalimaging system is f, and a minimum value among Abbe numbers of all lenselements of the optical imaging system is Vmin, the following conditionsare satisfied:3.50<TL/f<5.0; andVmin<22.5.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be better understood by reading the followingdetailed description of the embodiments, with reference made to theaccompanying drawings as follows:

FIG. 1 is a schematic view of an image capturing unit according to the1st embodiment of the present disclosure;

FIG. 2 shows spherical aberration curves, astigmatic field curves and adistortion curve of the image capturing unit according to the 1stembodiment;

FIG. 3 is a schematic view of an image capturing unit according to the2nd embodiment of the present disclosure;

FIG. 4 shows spherical aberration curves, astigmatic field curves and adistortion curve of the image capturing unit according to the 2ndembodiment;

FIG. 5 is a schematic view of an image capturing unit according to the3rd embodiment of the present disclosure;

FIG. 6 shows spherical aberration curves, astigmatic field curves and adistortion curve of the image capturing unit according to the 3rdembodiment;

FIG. 7 is a schematic view of an image capturing unit according to the4th embodiment of the present disclosure;

FIG. 8 shows spherical aberration curves, astigmatic field curves and adistortion curve of the image capturing unit according to the 4thembodiment;

FIG. 9 is a schematic view of an image capturing unit according to the5th embodiment of the present disclosure;

FIG. 10 shows spherical aberration curves, astigmatic field curves and adistortion curve of the image capturing unit according to the 5thembodiment;

FIG. 11 is a schematic view of an image capturing unit according to the6th embodiment of the present disclosure;

FIG. 12 shows spherical aberration curves, astigmatic field curves and adistortion curve of the image capturing unit according to the 6thembodiment;

FIG. 13 is a schematic view of an image capturing unit according to the7th embodiment of the present disclosure;

FIG. 14 shows spherical aberration curves, astigmatic field curves and adistortion curve of the image capturing unit according to the 7thembodiment;

FIG. 15 is a schematic view of an image capturing unit according to the8th embodiment of the present disclosure;

FIG. 16 shows spherical aberration curves, astigmatic field curves and adistortion curve of the image capturing unit according to the 8thembodiment;

FIG. 17 is a perspective view of an image capturing unit according tothe 9th embodiment of the present disclosure;

FIG. 18 is one perspective view of an electronic device according to the10th embodiment of the present disclosure;

FIG. 19 is another perspective view of the electronic device in FIG. 18;

FIG. 20 is a block diagram of the electronic device in FIG. 18; and

FIG. 21 shows a schematic view of Yc22, Yi42, a critical point of theimage-side surface of the second lens element, and inflection points ofthe image-side surface of the fourth lens element according to the 1stembodiment of the present disclosure.

DETAILED DESCRIPTION

An optical imaging system includes four lens elements. The four lenselements are, in order from an object side to an image side, a firstlens element, a second lens element, a third lens element and a fourthlens element. Each of the four lens elements of the optical imagingsystem has an object-side surface facing toward the object side and animage-side surface facing toward the image side.

The first lens element can have negative refractive power. Therefore, itis favorable for enlarging the viewing angle of the optical imagingsystem so as to increase the image identification area. The object-sidesurface of the first lens element is concave in a paraxial regionthereof. Therefore, it is favorable for distributing negative refractivepower on the object side of the optical imaging system so as to preventexcessive aberrations caused by an overly curved lens surface of asingle lens element. The object-side surface of the first lens elementcan be aspheric and can have at least one convex shape in an off-axisregion thereof. Therefore, it is favorable for controlling the totalthickness of the first lens element so as to minimize the size of thefirst lens element, and thereby ensure the miniaturization of theoptical imaging system.

The image-side surface of the second lens element can be concave in aparaxial region thereof. Therefore, it is favorable for correctingdistortion and astigmatism.

The third lens element can have positive refractive power. Therefore, itis favorable for controlling the angle of incidence on the image surfaceso as to ensure sufficient light on the image surface, therebyincreasing illuminance on the peripheral region of the image surface toensure good results from peripheral image identifications. Theobject-side surface of the third lens element can be convex in aparaxial region thereof so as to strengthen the light convergingcapability of the optical imaging system. When the image-side surface ofthe third lens element is also convex in a paraxial region thereof, itis favorable for providing significant light converging capability so asto control the size of the lens unit, thereby making the optical imagingsystem applicable to various applications.

The fourth lens element can have negative refractive power. Therefore,it is favorable for effectively correcting chromatic aberration so as toensure good image quality. The object-side surface of the fourth lenselement can be concave in a paraxial region thereof. Therefore, it isfavorable for balancing the shapes of the object-side surface and theimage-side surface of the fourth lens element so as to properlydistribute the refractive power of the fourth lens element, therebypreventing excessive aberrations. The image-side surface of the fourthlens element can be concave in a paraxial region thereof. Therefore, itis favorable for reducing the back focal length of the optical imagingsystem so as to obtain a compact configuration. The image-side surfaceof the fourth lens element can have at least one inflection point.Therefore, it is favorable for effectively correcting off-axisaberrations and reducing the size of the lens unit. Please refer to FIG.21, which shows a schematic view of inflection points P of theimage-side surface 142 of the fourth lens element 140 according to the1st embodiment of the present disclosure. The inflection points on theimage-side surface of the fourth lens element in FIG. 21 are onlyexemplary. The other lens surfaces of the four lens elements may alsohave one or more inflection points.

When an axial distance between the object-side surface of the first lenselement and an image surface is TL, and a focal length of the opticalimaging system is f, the following condition is satisfied:3.0<TL/f<10.0. Therefore, it is favorable for balancing between thetotal track length and the field of view of the optical imaging systemso as to meet various application requirements. Moreover, the followingcondition can also be satisfied: 3.0<TL/f<6.0. Moreover, the followingcondition can also be satisfied: 3.50<TL/f<5.0.

When an axial distance between the first lens element and the secondlens element is T12, an axial distance between the second lens elementand the third lens element is T23, and an axial distance between thethird lens element and the fourth lens element is T34, at least one ofthe following conditions can be satisfied: T23<T12; and T34<T12.Therefore, it is favorable for providing sufficient space on the objectside of the optical imaging system so as to moderate the incident angleat a wide field of view, thereby minimizing aberrations.

When the focal length of the optical imaging system is f, and a focallength of the second lens element is f2, the following condition can besatisfied: −3.0<f/f2<0.40. Therefore, it is favorable for the secondlens element to provide functionality of a correction lens so as tobalance image quality for different off-axis regions. Moreover, thefollowing condition can also be satisfied: −1.0<f/f2<0.25.

When the axial distance between the object-side surface of the firstlens element and the image surface is TL, a maximum image height of theoptical imaging system (half of a diagonal length of an effectivephotosensitive area of an image sensor) is ImgH, the following conditioncan be satisfied: 1.50<TL/ImgH<4.20. Therefore, it is favorable forhaving a proper light-receiving area for ensuring sufficient imagebrightness while miniaturizing the optical imaging system. Moreover, thefollowing condition can also be satisfied: 2.0<TL/ImgH<3.50.

According to the present disclosure, the optical imaging system furtherincludes an aperture stop. When an axial distance between the aperturestop and the image-side surface of the fourth lens element is SD, and anaxial distance between the object-side surface of the first lens elementand the image-side surface of the fourth lens element is TD, thefollowing condition can be satisfied: 0.34<SD/TD<1.20. Therefore, it isfavorable for positioning the aperture stop and balancing between thefield of view and the total track length of the optical imaging system.Moreover, the following condition can also be satisfied:0.40<SD/TD<0.90. Moreover, the following condition can also besatisfied: 0.45<SD/TD<0.65.

When a curvature radius of the object-side surface of the first lenselement is R1, and a curvature radius of the image-side surface of thefirst lens element is R2, the following condition can be satisfied:(R1+R2)/(R1−R2)<0.90. Therefore, it is favorable for increasing theviewing angle of the optical imaging system so as to capture more imagedata. Moreover, the following condition can also be satisfied:−10.0<(R1+R2)/(R1−R2)<0.50. Moreover, the following condition can alsobe satisfied: −5.0<(R1+R2)/(R1−R2)<0.

When the focal length of the optical imaging system is f, and a focallength of the fourth lens element is f4, the following condition can besatisfied: −3.0<f/f4<−0.55. Therefore, it is favorable for convergenceof the focal points of different wavelengths for the optical imagingsystem to be applicable to more applications.

Moreover, the following condition can also be satisfied:−1.6<f/f4<−0.70.

When a minimum value among Abbe numbers of all lens elements of theoptical imaging system is Vmin, the following condition can besatisfied: Vmin <22.5. Therefore, it is favorable for the lens elementsto control the light path so as to increase the design flexibility forsatisfying high-end product specifications. Moreover, the followingcondition can also be satisfied: 10.0<Vmin<20.5.

When a central thickness of the first lens element is CT1, a centralthickness of the second lens element is CT2, a central thickness of thethird lens element is CT3, and a central thickness of the fourth lenselement is CT4, at least one of the following conditions can besatisfied: CT1<CT3; CT2<CT3; and CT4<CT3. Therefore, it is favorable forbalancing the thickness configuration of the lens elements for therefractive power distribution of the optical imaging system.

When an Abbe number of the fourth lens element is V4, the followingcondition can be satisfied: 10.0<V4<23.0. Therefore, it is favorable forthe optical imaging system to obtain high image quality when operatedwithin different wavelength ranges, and thereby increase colorsaturation in images.

According to the present disclosure, the aperture stop can be disposedbetween the first lens element and the second lens element. Therefore,it is favorable for balancing between the size and the viewing angle ofthe optical imaging system so as to obtain a wide field of view and acompact configuration.

When the focal length of the optical imaging system is f, and thecurvature radius of the object-side surface of the first lens element isR1, the following condition can be satisfied: −2.0<f/R1<−0.50.Therefore, it is favorable for providing a retrofocus configuration soas to increase the light receiving area.

When the maximum image height of the optical imaging system is ImgH, andthe focal length of the optical imaging system is f, the followingcondition can be satisfied: 1.20<ImgH/f<3.0. Therefore, it is favorablefor increasing the light receiving area such that the optical imagingsystem is applicable to various applications.

When the focal length of the optical imaging system is f, and anentrance pupil diameter of the optical imaging system is EPD, thefollowing condition can be satisfied: 1.0<f/EPD<2.25. Therefore, it isfavorable for adjusting the entrance pupil diameter so as to control theamount of incident light to increase image brightness.

When the axial distance between the object-side surface of the firstlens element and the image surface is TL, the following condition can besatisfied: 0.50 [mm]<TL<4.0 [mm]. Therefore, it is favorable forcontrolling the total track length of the optical imaging system so asto achieve compactness.

When the axial distance between the object-side surface of the firstlens element and the image-side surface of the fourth lens element isTD, and the axial distance between the first lens element and the secondlens element is T12, the following condition can be satisfied:1.20<TD/T12<3.50. Therefore, it is favorable for providing sufficientspace between the first and second lens elements so as to modulate thelight path at a large field of view to prevent significant distortion.

When a curvature radius of the object-side surface of the second lenselement is R3, and a curvature radius of the image-side surface of thesecond lens element is R4, the following condition can be satisfied:−0.45<(R3−R4)/(R3+R4)<1.45. Therefore, it is favorable for balancing theshapes of lens surfaces on the object side and image side of the secondlens element so as to improve the symmetry of the optical imagingsystem. Moreover, the following condition can also be satisfied:−0.45<(R3−R4)/(R3+R4)<0.65.

When the focal length of the optical imaging system is f, and a focallength of the third lens element is f3, the following condition can besatisfied: 1.0 <f/f3<3.50. Therefore, it is favorable for the lightconverging capability of the third lens element so as to control thesize of the optical imaging system.

When the central thickness of the second lens element is CT2, and thecentral thickness of the third lens element is CT3, the followingcondition can be satisfied: 0.10<CT2/CT3<1.50. Therefore, it isfavorable for balancing the ratio between the thicknesses of the secondand third lens elements so as to properly allocate the space in theoptical imaging system, thereby improving image quality. Moreover, thefollowing condition can also be satisfied: 0.70<CT2/CT3<1.10.

When a curvature radius of the object-side surface of the third lenselement is R5, and a curvature radius of the image-side surface of thethird lens element is R6, the following condition can be satisfied:−0.80<(R5+R6)/(R5−R6)<0.80. Therefore, it is favorable for preventing anoverly large curvature of a single lens surface of the third lenselement and thus avoiding excessive aberrations so as to correctspherical aberrations. Moreover, the following condition can also besatisfied: −0.30<(R5+R6)/(R5−R6)<0.50.

When a vertical distance between a critical point on the image-sidesurface of the second lens element and an optical axis is Yc22, and thefocal length of the optical imaging system is f, the following conditioncan be satisfied: 0.05<Yc22/f<0.70. Therefore, it is favorable forcorrecting off-axis aberrations such as coma and astigmatism whilereducing the total track length of the optical imaging system. Pleaserefer to FIG. 21, which shows a schematic view of Yc22 and a criticalpoint C of the image-side surface 122 of the second lens element 120according to the 1st embodiment of the present disclosure. The criticalpoint on the image-side surface of the second lens element in FIG. 21 isonly exemplary. The other lens surfaces of the four lens elements mayalso have one or more critical points.

When a vertical distance between an inflection point on the image-sidesurface of the fourth lens element and the optical axis is Yi42, and thefocal length of the optical imaging system is f, the image-side surfaceof the fourth lens element can have at least one inflection pointsatisfying the following condition: 0.10<Yi42/f<1.20. Therefore, it isfavorable for reducing the back focal length of the optical imagingsystem so as to achieve compactness, and correcting field curvature soas to flatten the Petzval surface of the optical imaging system. Pleaserefer to FIG. 21, which shows a schematic view of Yi42 according to the1st embodiment of the present disclosure.

According to the present disclosure, the aforementioned features andconditions can be utilized in numerous combinations so as to achievecorresponding effects.

According to the present disclosure, the lens elements of the opticalimaging system can be made of either glass or plastic material. When thelens elements are made of glass material, the refractive powerdistribution of the optical imaging system may be more flexible. Theglass lens element can either be made by grinding or molding. When thelens elements are made of plastic material, the manufacturing cost canbe effectively reduced. Furthermore, surfaces of each lens element canbe arranged to be aspheric, which allows more control variables foreliminating aberrations thereof, the required number of the lenselements can be reduced, and the total track length of the opticalimaging system can be effectively shortened. The aspheric surfaces maybe formed by plastic injection molding or glass molding.

According to the present disclosure, when a lens surface is aspheric, itmeans that the lens surface has an aspheric shape throughout itsoptically effective area, or a portion(s) thereof.

According to the present disclosure, one or more of the lens elements'material may optionally include an additive which alters the lenselements' transmittance in a specific range of wavelength for areduction in unwanted stray light or colour deviation. For example, theadditive may optionally filter out light in the wavelength range of 600nm to 800 nm to reduce excessive red light and/or near infrared light;or may optionally filter out light in the wavelength range of 350 nm to450 nm to reduce excessive blue light and/or near ultraviolet light frominterfering the final image. The additive may be homogeneously mixedwith a plastic material to be used in manufacturing a mixed-materiallens element by injection molding.

According to the present disclosure, each of an object-side surface andan image-side surface has a paraxial region and an off-axis region. Theparaxial region refers to the region of the surface where light raystravel close to the optical axis, and the off-axis region refers to theregion of the surface away from the paraxial region. Particularly,unless otherwise stated, when the lens element has a convex surface, itindicates that the surface is convex in the paraxial region thereof;when the lens element has a concave surface, it indicates that thesurface is concave in the paraxial region thereof. Moreover, when aregion of refractive power or focus of a lens element is not defined, itindicates that the region of refractive power or focus of the lenselement is in the paraxial region thereof.

According to the present disclosure, an inflection point is a point onthe surface of the lens element at which the surface changes fromconcave to convex, or vice versa. A critical point is a non-axial pointof the lens surface where its tangent is perpendicular to the opticalaxis.

According to the present disclosure, an image surface of the opticalimaging system, based on the corresponding image sensor, can be flat orcurved, especially a curved surface being concave facing towards theobject side of the optical imaging system.

According to the present disclosure, an image correction unit, such as afield flattener, can be optionally disposed between the lens elementclosest to the image side of the optical imaging system and the imagesurface for correction of aberrations such as field curvature. Theoptical properties of the image correction unit, such as curvature,thickness, index of refraction, position and surface shape (convex orconcave surface with spherical, aspheric, diffractive or Fresnel types),can be adjusted according to the design of an image capturing unit. Ingeneral, a preferable image correction unit is, for example, a thintransparent element having a concave object-side surface and a planarimage-side surface, and the thin transparent element is disposed nearthe image surface.

According to the present disclosure, the optical imaging system caninclude at least one stop, such as an aperture stop, a glare stop or afield stop. Said glare stop or said field stop is set for eliminatingthe stray light and thereby improving image quality thereof.

According to the present disclosure, an aperture stop can be configuredas a front stop or a middle stop. A front stop disposed between animaged object and the first lens element can provide a longer distancebetween an exit pupil of the optical imaging system and the imagesurface to produce a telecentric effect, and thereby improves theimage-sensing efficiency of an image sensor (for example, CCD or CMOS).A middle stop disposed between the first lens element and the imagesurface is favorable for enlarging the viewing angle of the opticalimaging system and thereby provides a wider field of view for the same.

According to the present disclosure, the optical imaging system caninclude an aperture control unit. The aperture control unit may be amechanical component or a light modulator, which can control the sizeand shape of the aperture through electricity or electrical signals. Themechanical component can include a movable member, such as a bladeassembly or a light baffle. The light modulator can include a shieldingelement, such as a filter, an electrochromic material or aliquid-crystal layer. The aperture control unit controls the amount ofincident light or exposure time to enhance the capability of imagequality adjustment. In addition, the aperture control unit can be theaperture stop of the present disclosure, which changes the f-number toobtain different image effects, such as the depth of field or lensspeed.

According to the above description of the present disclosure, thefollowing specific embodiments are provided for further explanation.

1st Embodiment

FIG. 1 is a schematic view of an image capturing unit according to the1st embodiment of the present disclosure. FIG. 2 shows, in order fromleft to right, spherical aberration curves, astigmatic field curves anda distortion curve of the image capturing unit according to the 1stembodiment. In FIG. 1, the image capturing unit includes the opticalimaging system (its reference numeral is omitted) of the presentdisclosure and an image sensor 170. The optical imaging system includes,in order from an object side to an image side, a first lens element 110,an aperture stop 100, a second lens element 120, a third lens element130, a stop 101, a fourth lens element 140, a cover glass 150 and animage surface 160. The optical imaging system includes four lenselements (110, 120, 130 and 140) with no additional lens elementdisposed between each of the adjacent four lens elements.

The first lens element 110 with negative refractive power has anobject-side surface 111 being concave in a paraxial region thereof andan image-side surface 112 being concave in a paraxial region thereof.The first lens element 110 is made of plastic material and has theobject-side surface 111 and the image-side surface 112 being bothaspheric. The object-side surface 111 of the first lens element 110 hasat least one convex shape in an off-axis region thereof.

The second lens element 120 with negative refractive power has anobject-side surface 121 being convex in a paraxial region thereof and animage-side surface 122 being concave in a paraxial region thereof. Thesecond lens element 120 is made of plastic material and has theobject-side surface 121 and the image-side surface 122 being bothaspheric. The image-side surface 122 of the second lens element 120 hasat least one critical point in an off-axis region thereof.

The third lens element 130 with positive refractive power has anobject-side surface 131 being convex in a paraxial region thereof and animage-side surface 132 being convex in a paraxial region thereof. Thethird lens element 130 is made of plastic material and has theobject-side surface 131 and the image-side surface 132 being bothaspheric.

The fourth lens element 140 with negative refractive power has anobject-side surface 141 being concave in a paraxial region thereof andan image-side surface 142 being concave in a paraxial region thereof.The fourth lens element 140 is made of plastic material and has theobject-side surface 141 and the image-side surface 142 being bothaspheric. The image-side surface 142 of the fourth lens element 140 hasat least one inflection point.

The cover glass 150 is made of glass material and located between thefourth lens element 140 and the image surface 160, and will not affectthe focal length of the optical imaging system. The image sensor 170 isdisposed on or near the image surface 160 of the optical imaging system.

The equation of the aspheric surface profiles of the aforementioned lenselements of the 1st embodiment is expressed as follows:

${{X(Y)} = {{\left( {Y^{2}/R} \right)/\left( {1 + {{sqrt}\left( {1 - {\left( {1 + k} \right) \times \left( {Y/R} \right)^{2}}} \right)}} \right)} + {\sum\limits_{i}{({Ai}) \times \left( Y^{i} \right)}}}},$where,

X is the relative distance between a point on the aspheric surfacespaced at a distance Y from an optical axis and the tangential plane atthe aspheric surface vertex on the optical axis;

Y is the vertical distance from the point on the aspheric surface to theoptical axis;

R is the curvature radius;

k is the conic coefficient; and

Ai is the i-th aspheric coefficient, and in the embodiments, i may be,but is not limited to, 4, 6, 8, 10, 12, 14 and 16.

In the optical imaging system of the image capturing unit according tothe 1st embodiment, when a focal length of the optical imaging system isf, an f-number of the optical imaging system is Fno, and half of amaximum field of view of the optical imaging system is HFOV, theseparameters have the following values: f=0.82 millimeters (mm), Fno=2.04,HFOV=57.3 degrees (deg.).

When an Abbe number of the fourth lens element 140 is V4, the followingcondition is satisfied: V4=20.40.

When a minimum value among Abbe numbers of all lens elements of theoptical imaging system is Vmin, the following condition is satisfied:Vmin=20.40. In this embodiment, among the first lens element 110, thesecond lens element 120, the third lens element 130 and the fourth lenselement 140, the Abbe number of the fourth lens element 140 is smallerthan the Abbe numbers of the other lens elements, and Vmin is equal tothe Abbe number of the fourth lens element 140.

When a central thickness of the second lens element 120 is CT2, and acentral thickness of the third lens element 130 is CT3, the followingcondition is satisfied: CT2/CT3=0.80.

When the focal length of the optical imaging system is f, and acurvature radius of the object-side surface 111 of the first lenselement 110 is R1, the following condition is satisfied: f/R1=−0.63.

When the curvature radius of the object-side surface 111 of the firstlens element 110 is R1, and a curvature radius of the image-side surface112 of the first lens element 110 is R2, the following condition issatisfied: (R1+R2)/(R1−R2)=−0.55.

When a curvature radius of the object-side surface 121 of the secondlens element 120 is R3, and a curvature radius of the image-side surface122 of the second lens element 120 is R4, the following condition issatisfied:(R3−R4)/(R3+R4)=0.23.

When a curvature radius of the object-side surface 131 of the third lenselement 130 is R5, and a curvature radius of the image-side surface 132of the third lens element 130 is R6, the following condition issatisfied: (R5+R6)/(R5−R6)=0.05.

When the focal length of the optical imaging system is f, and a focallength of the second lens element 120 is f2, the following condition issatisfied: f/f2=−0.10.

When the focal length of the optical imaging system is f, and a focallength of the third lens element 130 is f3, the following condition issatisfied: f/f3=1.48.

When the focal length of the optical imaging system is f, and a focallength of the fourth lens element 140 is f4, the following condition issatisfied: f/f4=−1.03.

When an axial distance between the aperture stop 100 and the image-sidesurface 142 of the fourth lens element 140 is SD, and an axial distancebetween the object-side surface 111 of the first lens element 110 andthe image-side surface 142 of the fourth lens element 140 is TD, thefollowing condition is satisfied: SD/TD=0.55.

When the axial distance between the object-side surface 111 of the firstlens element 110 and the image-side surface 142 of the fourth lenselement 140 is TD, and an axial distance between the first lens element110 and the second lens element 120 is T12, the following condition issatisfied: TD/T12=3.13. In this embodiment, an axial distance betweentwo adjacent lens elements is an air gap in a paraxial region betweenthe two adjacent lens elements.

When a maximum image height of the optical imaging system is ImgH, andthe focal length of the optical imaging system is f, the followingcondition is satisfied: ImgH/f=1.46.

When an axial distance between the object-side surface 111 of the firstlens element 110 and the image surface 160 is TL, and the maximum imageheight of the optical imaging system is ImgH, the following condition issatisfied: TL/ImgH=2.82.

When the axial distance between the object-side surface 111 of the firstlens element 110 and the image surface 160 is TL, and the focal lengthof the optical imaging system is f, the following condition issatisfied: TL/f=4.12.

When the axial distance between the object-side surface 111 of the firstlens element 110 and the image surface 160 is TL, the followingcondition is satisfied: TL=3.39 [mm].

When the focal length of the optical imaging system is f, and anentrance pupil diameter of the optical imaging system is EPD, thefollowing condition is satisfied: f/EPD=2.04.

When a vertical distance between the critical point on the image-sidesurface 122 of the second lens element 120 and the optical axis is Yc22,and the focal length of the optical imaging system is f, the followingcondition is satisfied: Yc22/f=0.22.

When a vertical distance between the inflection point(s) on theimage-side surface 142 of the fourth lens element 140 and the opticalaxis is Yi42, and the focal length of the optical imaging system is f,the following condition is satisfied: Yi42/f=0.249, 0.510 and 0.722. Inthis embodiment, the image-side surface 142 of the fourth lens element140 has three inflection points, and the ratios of the verticaldistances between the three inflection points and the optical axis tothe focal length of the optical imaging system are 0.249, 0.510 and0.722, respectively.

The detailed optical data of the 1st embodiment are shown in Table 1 andthe aspheric surface data are shown in Table 2 below.

TABLE 1 1st Embodiment f = 0.82 mm, Fno = 2.04, HFOV = 57.3 deg. Surface# Curvature Radius Thickness Material Index Abbe # Focal Length 0 ObjectPlano 400.000 1 Lens 1 −1.300 (ASP) 0.385 Plastic 1.545 56.1 −1.81 24.505 (ASP) 0.757 3 Ape. Stop Plano 0.050 4 Lens 2 1.982 (ASP) 0.451Plastic 1.534 55.9 −7.89 5 1.242 (ASP) 0.043 6 Lens 3 0.505 (ASP) 0.564Plastic 1.544 56.0 0.56 7 −0.457 (ASP) −0.238 8 Stop Plano 0.268 9 Lens4 −1.424 (ASP) 0.247 Plastic 1.660 20.4 −0.80 10 0.895 (ASP) 0.430 11Cover Glass Plano 0.210 Glass 1.517 64.2 — 12 Plano 0.224 13 Image Plano— Note: Reference wavelength is 587.6 nm (d-line). An effective radiusof the stop 101 (Surface 8) is 0.590 mm.

TABLE 2 Aspheric Coefficients Surface # 1 2 4 5 k = −2.4891E+01 5.3515E+01 −4.1192E+01 −1.5944E+01 A4 =  9.6272E−01  2.0772E+00 4.1124E−02 −6.6828E+00 A6 = −2.0758E+00  1.5733E+01 −1.1235E+01 3.6789E+01 A8 =  3.9698E+00 −2.9497E+02  1.1066E+02 −2.5610E+02 A10 =−5.1167E+00  2.4260E+03 −8.9090E+02  1.1269E+03 A12 =  4.1065E+00−1.0445E+04  1.5359E+03 −2.6382E+03 A14 = −1.7948E+00  2.3156E+04 — 2.2638E+03 A16 =  3.1620E−01 −2.0502E+04 — — Surface # 6 7 9 10 k =−5.8919E+00 −9.1655E+00 −2.3154E−01 −1.5511E+01 A4 = −9.2420E−01 2.1002E−01  3.3284E+00 −9.8176E−01 A6 =  2.0289E+00 −1.1470E+01−7.3002E+01 −2.2525E+00 A8 = −4.4042E+01  2.4843E+01  5.0811E+02 3.8380E+01 A10 =  1.3618E+02  9.4005E+01 −1.8358E+03 −1.3820E+02 A12 =−9.6911E+01 −4.5190E+02  3.8795E+03  2.3590E+02 A14 = —  4.9837E+02−4.7966E+03 −2.0153E+02 A16 = — —  2.7508E+03  6.9672E+01

In Table 1, the curvature radius, the thickness and the focal length areshown in millimeters (mm). Surface numbers 0-13 represent the surfacessequentially arranged from the object side to the image side along theoptical axis. In Table 2, k represents the conic coefficient of theequation of the aspheric surface profiles. A4-16 represent the asphericcoefficients ranging from the 4th order to the 16th order. The tablespresented below for each embodiment are the corresponding schematicparameter and aberration curves, and the definitions of the tables arethe same as Table 1 and Table 2 of the 1st embodiment. Therefore, anexplanation in this regard will not be provided again.

2nd Embodiment

FIG. 3 is a schematic view of an image capturing unit according to the2nd embodiment of the present disclosure. FIG. 4 shows, in order fromleft to right, spherical aberration curves, astigmatic field curves anda distortion curve of the image capturing unit according to the 2ndembodiment. In FIG. 3, the image capturing unit includes the opticalimaging system (its reference numeral is omitted) of the presentdisclosure and an image sensor 270. The optical imaging system includes,in order from an object side to an image side, a first lens element 210,an aperture stop 200, a second lens element 220, a third lens element230, a stop 201, a fourth lens element 240, a cover glass 250 and animage surface 260. The optical imaging system includes four lenselements (210, 220, 230 and 240) with no additional lens elementdisposed between each of the adjacent four lens elements.

The first lens element 210 with negative refractive power has anobject-side surface 211 being concave in a paraxial region thereof andan image-side surface 212 being concave in a paraxial region thereof.The first lens element 210 is made of plastic material and has theobject-side surface 211 and the image-side surface 212 being bothaspheric. The object-side surface 211 of the first lens element 210 hasat least one convex shape in an off-axis region thereof.

The second lens element 220 with positive refractive power has anobject-side surface 221 being convex in a paraxial region thereof and animage-side surface 222 being concave in a paraxial region thereof. Thesecond lens element 220 is made of plastic material and has theobject-side surface 221 and the image-side surface 222 being bothaspheric. The image-side surface 222 of the second lens element 220 hasat least one critical point in an off-axis region thereof.

The third lens element 230 with positive refractive power has anobject-side surface 231 being convex in a paraxial region thereof and animage-side surface 232 being convex in a paraxial region thereof. Thethird lens element 230 is made of plastic material and has theobject-side surface 231 and the image-side surface 232 being bothaspheric.

The fourth lens element 240 with negative refractive power has anobject-side surface 241 being concave in a paraxial region thereof andan image-side surface 242 being concave in a paraxial region thereof.The fourth lens element 240 is made of plastic material and has theobject-side surface 241 and the image-side surface 242 being bothaspheric. The image-side surface 242 of the fourth lens element 240 hasat least one inflection point.

The cover glass 250 is made of glass material and located between thefourth lens element 240 and the image surface 260, and will not affectthe focal length of the optical imaging system. The image sensor 270 isdisposed on or near the image surface 260 of the optical imaging system.

The detailed optical data of the 2nd embodiment are shown in Table 3 andthe aspheric surface data are shown in Table 4 below.

TABLE 3 2nd Embodiment f = 0.82 mm, Fno = 2.04, HFOV = 55.0 deg. Surface# Curvature Radius Thickness Material Index Abbe # Focal Length 0 ObjectPlano 400.000 1 Lens 1 −1.300 (ASP) 0.387 Plastic 1.545 56.1 −1.81 24.505 (ASP) 0.758 3 Ape. Stop Plano 0.048 4 Lens 2 1.997 (ASP) 0.467Plastic 1.534 55.9 15.90 5 2.398 (ASP) 0.047 6 Lens 3 0.612 (ASP) 0.520Plastic 1.544 56.0 0.59 7 −0.465 (ASP) −0.237 8 Stop Plano 0.268 9 Lens4 −1.421 (ASP) 0.252 Plastic 1.660 20.4 −0.81 10 0.909 (ASP) 0.430 11Cover Glass Plano 0.210 Glass 1.517 64.2 — 12 Plano 0.228 13 Image Plano— Note: Reference wavelength is 587.6 nm (d-line). An effective radiusof the stop 201 (Surface 8) is 0.590 mm.

TABLE 4 Aspheric Coefficients Surface # 1 2 4 5 k = −2.3591E+01 5.2751E+01 −3.2818E+01 −1.0660E+01 A4 =  9.6033E−01  2.0063E+00−3.0645E−01 −5.3189E+00 A6 = −2.0479E+00  1.6150E+01 −3.8694E+00 1.1570E+01 A8 =  3.8572E+00 −2.9197E+02 −9.4723E+00 −2.3019E+01 A10 =−4.8723E+00  2.3746E+03  3.1791E+01 −5.6631E+01 A12 =  3.8257E+00−1.0176E+04 −1.3654E+03  5.1078E+02 A14 = −1.6323E+00  2.2559E+04 —−1.2168E+03 A16 =  2.7899E−01 −2.0035E+04 — — Surface # 6 7 9 10 k =−6.0078E+00 −9.2765E+00 −2.0758E−01 −1.5875E+01 A4 = −7.4817E−01 3.9044E−01  3.2501E+00 −1.0140E+00 A6 = −3.3722E+00 −1.4687E+01−7.2681E+01 −1.3245E+00 A8 = −4.4766E+00  4.3983E+01  5.1304E+02 3.2284E+01 A10 =  1.9884E+01  5.1225E+01 −1.8727E+03 −1.2084E+02 A12 = 2.9065E+01 −4.3911E+02  3.9568E+03  2.1073E+02 A14 = —  5.4789E+02−4.8205E+03 −1.8297E+02 A16 = — —  2.7018E+03  6.4050E+01

In the 2nd embodiment, the equation of the aspheric surface profiles ofthe aforementioned lens elements is the same as the equation of the 1stembodiment. Also, the definitions of these parameters shown in thefollowing table are the same as those stated in the 1st embodiment withcorresponding values for the 2nd embodiment, so an explanation in thisregard will not be provided again.

Moreover, these parameters can be calculated from Table 3 and Table 4 asthe following values and satisfy the following conditions:

2nd Embodiment f [mm] 0.82 f/f3 1.41 Fno 2.04 f/f4 −1.02 HFOV [deg.]55.0 SD/TD 0.54 V4 20.40 TD/T12 3.12 Vmin 20.40 ImgH/f 1.40 CT2/CT3 0.90TL/ImgH 2.94 f/R1 −0.63 TL/f 4.10 (R1 + R2)/(R1 − R2) −0.55 TL [mm] 3.38(R3 − R4)/(R3 + R4) −0.09 f/EPD 2.04 (R5 + R6)/(R5 − R6) 0.14 Yc22/f0.18 f/f2 0.05 Yi42/f 0.249/0.516/0.723

3rd Embodiment

FIG. 5 is a schematic view of an image capturing unit according to the3rd embodiment of the present disclosure. FIG. 6 shows, in order fromleft to right, spherical aberration curves, astigmatic field curves anda distortion curve of the image capturing unit according to the 3rdembodiment. In FIG. 5, the image capturing unit includes the opticalimaging system (its reference numeral is omitted) of the presentdisclosure and an image sensor 370. The optical imaging system includes,in order from an object side to an image side, a first lens element 310,an aperture stop 300, a second lens element 320, a third lens element330, a stop 301, a fourth lens element 340, a cover glass 350 and animage surface 360. The optical imaging system includes four lenselements (310, 320, 330 and 340) with no additional lens elementdisposed between each of the adjacent four lens elements.

The first lens element 310 with negative refractive power has anobject-side surface 311 being concave in a paraxial region thereof andan image-side surface 312 being convex in a paraxial region thereof. Thefirst lens element 310 is made of plastic material and has theobject-side surface 311 and the image-side surface 312 being bothaspheric. The object-side surface 311 of the first lens element 310 hasat least one convex shape in an off-axis region thereof.

The second lens element 320 with positive refractive power has anobject-side surface 321 being convex in a paraxial region thereof and animage-side surface 322 being convex in a paraxial region thereof. Thesecond lens element 320 is made of plastic material and has theobject-side surface 321 and the image-side surface 322 being bothaspheric.

The third lens element 330 with positive refractive power has anobject-side surface 331 being convex in a paraxial region thereof and animage-side surface 332 being convex in a paraxial region thereof. Thethird lens element 330 is made of plastic material and has theobject-side surface 331 and the image-side surface 332 being bothaspheric.

The fourth lens element 340 with negative refractive power has anobject-side surface 341 being concave in a paraxial region thereof andan image-side surface 342 being concave in a paraxial region thereof.The fourth lens element 340 is made of plastic material and has theobject-side surface 341 and the image-side surface 342 being bothaspheric. The image-side surface 342 of the fourth lens element 340 hasat least one inflection point.

The cover glass 350 is made of glass material and located between thefourth lens element 340 and the image surface 360, and will not affectthe focal length of the optical imaging system. The image sensor 370 isdisposed on or near the image surface 360 of the optical imaging system.

The detailed optical data of the 3rd embodiment are shown in Table 5 andthe aspheric surface data are shown in Table 6 below.

TABLE 5 3rd Embodiment f = 0.76 mm, Fno = 2.04, HFOV = 58.4 deg. Surface# Curvature Radius Thickness Material Index Abbe # Focal Length 0 ObjectPlano 400.000 1 Lens 1 -0.861 (ASP) 0.400 Plastic 1.545 56.1 −2.10 2−4.024 (ASP) 0.888 3 Ape. Stop Plano 0.042 4 Lens 2 2.756 (ASP) 0.512Plastic 1.534 55.9 4.40 5 −14.891 (ASP) 0.093 6 Lens 3 0.684 (ASP) 0.582Plastic 1.544 56.0 0.62 7 −0.468 (ASP) −0.255 8 Stop Plano 0.285 9 Lens4 −0.946 (ASP) 0.275 Plastic 1.669 19.4 −0.71 10 1.078 (ASP) 0.430 11Cover Glass Plano 0.210 Glass 1.517 64.2 — 12 Plano 0.089 13 Image Plano— Note: Reference wavelength is 587.6 nm (d-line). An effective radiusof the stop 301 (Surface 8) is 0.587 mm.

TABLE 6 Aspheric Coefficients Surface # 1 2 4 5 k = −1.3382E+01−9.0000E+01  1.1104E+00 −9.0000E+01 A4 =  6.4734E−01  2.9030E+00−8.3525E−01 −4.7061E+00 A6 = −8.6487E−01 −1.4981E+01 −1.1049E+01 1.5881E+01 A8 =  8.9342E−01  9.5457E+01  1.1488E+02 −8.9570E+01 A10 =−6.2461E−01 −3.8296E+02 −1.0560E+03  3.3402E+02 A12 =  2.9387E−01 8.7757E+02  2.2512E+03 −5.0812E+02 A14 = −8.2745E−02 −1.0199E+03−3.9908E+02 −6.5446E+02 A16 =  9.9807E−03  4.6031E+02 —  1.8061E+03Surface # 6 7 9 10 k = −9.0335E+00 −7.8214E+00 −2.4426E+00 −1.6076E+01A4 = −3.5618E−01  1.3982E+00  4.4298E+00 −6.2579E−01 A6 = −1.2671E+00−3.4245E+01 −8.3641E+01 −5.6200E+00 A8 = −4.5008E+01  1.7688E+02 5.2582E+02  4.6266E+01 A10 =  2.2326E+02 −4.0401E+02 −1.5389E+03−1.3380E+02 A12 = −3.1903E+02  3.8043E+02  1.9956E+03  1.9193E+02 A14 = 1.0860E+02 −7.0554E+01 −4.3171E+02 −1.3829E+02 A16 = — — −9.4231E+02 3.9984E+01

In the 3rd embodiment, the equation of the aspheric surface profiles ofthe aforementioned lens elements is the same as the equation of the 1stembodiment. Also, the definitions of these parameters shown in thefollowing table are the same as those stated in the 1st embodiment withcorresponding values for the 3rd embodiment, so an explanation in thisregard will not be provided again.

Moreover, these parameters can be calculated from Table 5 and Table 6 asthe following values and satisfy the following conditions:

3rd Embodiment f [mm] 0.76 f/f3 1.22 Fno 2.04 f/f4 −1.06 HFOV [deg.]58.4 SD/TD 0.54 V4 19.44 TD/T12 3.03 Vmin 19.44 ImgH/f 1.55 CT2/CT3 0.88TL/ImgH 3.01 f/R1 −0.88 TL/f 4.67 (R1 + R2)/(R1 − R2) −1.54 TL [mm] 3.55(R3 − R4)/(R3 + R4) −1.45 f/EPD 2.04 (R5 + R6)/(R5 − R6) 0.19 Yc22/f —f/f2 0.17 Yi42/f 0.276/0.592/0.797

4th Embodiment

FIG. 7 is a schematic view of an image capturing unit according to the4th embodiment of the present disclosure. FIG. 8 shows, in order fromleft to right, spherical aberration curves, astigmatic field curves anda distortion curve of the image capturing unit according to the 4thembodiment. In FIG. 7, the image capturing unit includes the opticalimaging system (its reference numeral is omitted) of the presentdisclosure and an image sensor 470. The optical imaging system includes,in order from an object side to an image side, a first lens element 410,an aperture stop 400, a second lens element 420, a third lens element430, a stop 401, a fourth lens element 440, a cover glass 450 and animage surface 460. The optical imaging system includes four lenselements (410, 420, 430 and 440) with no additional lens elementdisposed between each of the adjacent four lens elements.

The first lens element 410 with negative refractive power has anobject-side surface 411 being concave in a paraxial region thereof andan image-side surface 412 being convex in a paraxial region thereof. Thefirst lens element 410 is made of plastic material and has theobject-side surface 411 and the image-side surface 412 being bothaspheric. The object-side surface 411 of the first lens element 410 hasat least one convex shape in an off-axis region thereof.

The second lens element 420 with negative refractive power has anobject-side surface 421 being convex in a paraxial region thereof and animage-side surface 422 being concave in a paraxial region thereof. Thesecond lens element 420 is made of plastic material and has theobject-side surface 421 and the image-side surface 422 being bothaspheric. The image-side surface 422 of the second lens element 420 hasat least one critical point in an off-axis region thereof.

The third lens element 430 with positive refractive power has anobject-side surface 431 being convex in a paraxial region thereof and animage-side surface 432 being convex in a paraxial region thereof. Thethird lens element 430 is made of plastic material and has theobject-side surface 431 and the image-side surface 432 being bothaspheric.

The fourth lens element 440 with negative refractive power has anobject-side surface 441 being convex in a paraxial region thereof and animage-side surface 442 being concave in a paraxial region thereof. Thefourth lens element 440 is made of plastic material and has theobject-side surface 441 and the image-side surface 442 being bothaspheric. The image-side surface 442 of the fourth lens element 440 hasat least one inflection point.

The cover glass 450 is made of glass material and located between thefourth lens element 440 and the image surface 460, and will not affectthe focal length of the optical imaging system. The image sensor 470 isdisposed on or near the image surface 460 of the optical imaging system.

The detailed optical data of the 4th embodiment are shown in Table 7 andthe aspheric surface data are shown in Table 8 below.

TABLE 7 4th Embodiment f = 0.92 mm, Fno = 2.06, HFOV = 52.2 deg. Surface# Curvature Radius Thickness Material Index Abbe # Focal Length 0 ObjectPlano 400.000 1 Lens 1 −1.109 (ASP) 0.263 Plastic 1.545 56.1 −3.92 2−2.498 (ASP) 0.824 3 Ape. Stop Plano 0.062 4 Lens 2 168.308 (ASP) 0.222Plastic 1.584 28.2 −2.44 5 1.413 (ASP) 0.068 6 Lens 3 0.667 (ASP) 0.752Plastic 1.544 56.0 0.63 7 −0.426 (ASP) −0.224 8 Stop Plano 0.254 9 Lens4 8.318 (ASP) 0.313 Plastic 1.680 18.4 −0.95 10 0.591 (ASP) 0.430 11Cover Glass Plano 0.210 Glass 1.517 64.2 — 12 Plano 0.201 13 Image Plano— Note: Reference wavelength is 587.6 nm (d-line). An effective radiusof the stop 401 (Surface 8) is 0.648 mm.

TABLE 8 Aspheric Coefficients Surface # 1 2 4 5 k = −1.3473E+01−3.8630E+01 −2.2051E+01  4.4821E−01 A4 =  7.7894E−01  1.4909E+00−2.2211E+00 −3.8818E+00 A6 = −1.0343E+00 −2.4302E+00  1.0964E+01 1.1926E+01 A8 =  1.1076E+00  7.3277E+00 −1.2713E+02 −5.7363E+00 A10 =−6.9955E−01 −2.3622E+01  5.7042E+02 −3.8270E+02 A12 =  2.3139E−01 5.3906E+01 −1.5514E+03  2.0656E+03 A14 = −9.6487E−03 −6.1455E+01 —−3.5971E+03 A16 = −1.4488E−02  2.5594E+01 — — Surface # 6 7 9 10 k =−2.6281E+00 −5.7027E+00 −9.0000E+01 −6.9470E+00 A4 = −1.3091E+00−1.2081E+00  1.7782E+00 −3.7501E−02 A6 =  7.9983E+00  9.2416E−01−3.3610E+01 −3.8623E+00 A8 = −2.9651E+01  1.7223E+01  2.2332E+02 1.8480E+01 A10 =  5.9436E+01 −9.1033E+01 −9.3864E+02 −4.8676E+01 A12 =−4.8599E+01  1.8832E+02  2.3179E+03  7.6874E+01 A14 = — −1.4289E+02−2.9644E+03 −6.5302E+01 A16 = — —  1.4911E+03  2.2511E+01

In the 4th embodiment, the equation of the aspheric surface profiles ofthe aforementioned lens elements is the same as the equation of the 1stembodiment. Also, the definitions of these parameters shown in thefollowing table are the same as those stated in the 1st embodiment withcorresponding values for the 4th embodiment, so an explanation in thisregard will not be provided again.

Moreover, these parameters can be calculated from Table 7 and Table 8 asthe following values and satisfy the following conditions:

4th Embodiment f [mm] 0.92 f/f3 1.46 Fno 2.06 f/f4 −0.97 HFOV [deg.]52.2 SD/TD 0.57 V4 18.40 TD/T12 2.86 Vmin 18.40 ImgH/f 1.25 CT2/CT3 0.30TL/ImgH 2.93 f/R1 −0.83 TL/f 3.66 (R1 + R2)/(R1 − R2) −2.60 TL [mm] 3.37(R3 − R4)/(R3 + R4) 0.98 f/EPD 2.06 (R5 + R6)/(R5 − R6) 0.22 Yc22/f 0.27f/f2 −0.38 Yi42/f 0.320/0.758/0.807

5th Embodiment

FIG. 9 is a schematic view of an image capturing unit according to the5th embodiment of the present disclosure. FIG. 10 shows, in order fromleft to right, spherical aberration curves, astigmatic field curves anda distortion curve of the image capturing unit according to the 5thembodiment. In FIG. 9, the image capturing unit includes the opticalimaging system (its reference numeral is omitted) of the presentdisclosure and an image sensor 570. The optical imaging system includes,in order from an object side to an image side, a first lens element 510,an aperture stop 500, a second lens element 520, a third lens element530, a stop 501, a fourth lens element 540, a cover glass 550 and animage surface 560. The optical imaging system includes four lenselements (510, 520, 530 and 540) with no additional lens elementdisposed between each of the adjacent four lens elements.

The first lens element 510 with negative refractive power has anobject-side surface 511 being concave in a paraxial region thereof andan image-side surface 512 being convex in a paraxial region thereof. Thefirst lens element 510 is made of plastic material and has theobject-side surface 511 and the image-side surface 512 being bothaspheric. The object-side surface 511 of the first lens element 510 hasat least one convex shape in an off-axis region thereof.

The second lens element 520 with negative refractive power has anobject-side surface 521 being concave in a paraxial region thereof andan image-side surface 522 being concave in a paraxial region thereof.The second lens element 520 is made of plastic material and has theobject-side surface 521 and the image-side surface 522 being bothaspheric. The image-side surface 522 of the second lens element 520 hasat least one critical point in an off-axis region thereof.

The third lens element 530 with positive refractive power has anobject-side surface 531 being convex in a paraxial region thereof and animage-side surface 532 being convex in a paraxial region thereof. Thethird lens element 530 is made of plastic material and has theobject-side surface 531 and the image-side surface 532 being bothaspheric.

The fourth lens element 540 with negative refractive power has anobject-side surface 541 being convex in a paraxial region thereof and animage-side surface 542 being concave in a paraxial region thereof. Thefourth lens element 540 is made of plastic material and has theobject-side surface 541 and the image-side surface 542 being bothaspheric. The image-side surface 542 of the fourth lens element 540 hasat least one inflection point.

The cover glass 550 is made of glass material and located between thefourth lens element 540 and the image surface 560, and will not affectthe focal length of the optical imaging system. The image sensor 570 isdisposed on or near the image surface 560 of the optical imaging system.

The detailed optical data of the 5th embodiment are shown in Table 9 andthe aspheric surface data are shown in Table 10 below.

TABLE 9 5th Embodiment f = 0.93 mm, Fno = 2.06, HFOV = 52.3 deg. Surface# Curvature Radius Thickness Material Index Abbe # Focal Length 0 ObjectPlano 400.000 1 Lens 1 −1.021 (ASP) 0.268 Plastic 1.545 56.1 −4.80 2−1.830 (ASP) 0.743 3 Ape. Stop Plano 0.066 4 Lens 2 −6.575 (ASP) 0.216Plastic 1.584 28.2 −2.22 5 1.633 (ASP) 0.057 6 Lens 3 0.688 (ASP) 0.744Plastic 1.544 56.0 0.64 7 −0.433 (ASP) −0.224 8 Stop Plano 0.254 9 Lens4 3.667 (ASP) 0.306 Plastic 1.680 18.4 −1.04 10 0.571 (ASP) 0.430 11Cover Glass Plano 0.210 Glass 1.517 64.2 — 12 Plano 0.197 13 Image Plano— Note: Reference wavelength is 587.6 nm (d-line). An effective radiusof the stop 501 (Surface 8) is 0.653 mm.

TABLE 10 Aspheric Coefficients Surface # 1 2 4 5 k = −1.2489E+01−2.8509E+01 −2.2051E+01  3.1029E+00 A4 =  7.3943E−01  1.3534E+00−1.9047E+00 −3.7266E+00 A6 = −9.9031E−01 −1.9600E+00  6.4315E+00 9.6070E+00 A8 =  1.0581E+00  3.4308E+00 −6.9181E+01  3.6021E+01 A10 =−6.2406E−01 −7.8171E+00  6.4677E+01 −7.4633E+02 A12 =  1.4680E−01 2.0244E+01  4.8706E+02  3.6100E+03 A14 =  4.4414E−02 −2.5907E+01 —−6.1634E+03 A16 = −2.7757E−02  1.1271E+01 — — Surface # 6 7 9 10 k =−2.6319E+00 −5.7038E+00 −8.5724E+01 −6.0486E+00 A4 = −1.5234E+00−1.4328E+00  1.6017E+00 −2.9254E−02 A6 =  9.5611E+00  1.5245E+00−2.9811E+01 −4.0804E+00 A8 = −3.5940E+01  1.8165E+01  1.8735E+02 1.8985E+01 A10 =  7.4425E+01 −1.0054E+02 −7.3514E+02 −4.7541E+01 A12 =−6.3740E+01  2.1317E+02  1.6867E+03  6.9842E+01 A14 = — −1.6601E+02−1.9884E+03 −5.4666E+01 A16 = — —  9.0556E+02  1.7309E+01

In the 5th embodiment, the equation of the aspheric surface profiles ofthe aforementioned lens elements is the same as the equation of the 1stembodiment. Also, the definitions of these parameters shown in thefollowing table are the same as those stated in the 1st embodiment withcorresponding values for the 5th embodiment, so an explanation in thisregard will not be provided again.

Moreover, these parameters can be calculated from Table 9 and Table 10as the following values and satisfy the following conditions:

5th Embodiment f [mm] 0.93 f/f3 1.46 Fno 2.06 f/f4 −0.90 HFOV [deg.]52.3 SD/TD 0.58 V4 18.40 TD/T12 3.00 Vmin 18.40 ImgH/f 1.24 CT2/CT3 0.29TL/ImgH 2.84 f/R1 −0.91 TL/f 3.51 (R1 + R2)/(R1 − R2) −3.52 TL [mm] 3.27(R3 − R4)/(R3 + R4) 1.66 f/EPD 2.06 (R5 + R6)/(R5 − R6) 0.23 Yc22/f 0.25f/f2 −0.42 Yi42/f 0.322/0.790/0.817

6th Embodiment

FIG. 11 is a schematic view of an image capturing unit according to the6th embodiment of the present disclosure. FIG. 12 shows, in order fromleft to right, spherical aberration curves, astigmatic field curves anda distortion curve of the image capturing unit according to the 6thembodiment. In FIG. 11, the image capturing unit includes the opticalimaging system (its reference numeral is omitted) of the presentdisclosure and an image sensor 670. The optical imaging system includes,in order from an object side to an image side, a first lens element 610,an aperture stop 600, a second lens element 620, a third lens element630, a stop 601, a fourth lens element 640, a cover glass 650 and animage surface 660. The optical imaging system includes four lenselements (610, 620, 630 and 640) with no additional lens elementdisposed between each of the adjacent four lens elements.

The first lens element 610 with negative refractive power has anobject-side surface 611 being concave in a paraxial region thereof andan image-side surface 612 being concave in a paraxial region thereof.The first lens element 610 is made of plastic material and has theobject-side surface 611 and the image-side surface 612 being bothaspheric. The object-side surface 611 of the first lens element 610 hasat least one convex shape in an off-axis region thereof.

The second lens element 620 with negative refractive power has anobject-side surface 621 being convex in a paraxial region thereof and animage-side surface 622 being concave in a paraxial region thereof. Thesecond lens element 620 is made of plastic material and has theobject-side surface 621 and the image-side surface 622 being bothaspheric. The image-side surface 622 of the second lens element 620 hasat least one critical point in an off-axis region thereof.

The third lens element 630 with positive refractive power has anobject-side surface 631 being convex in a paraxial region thereof and animage-side surface 632 being convex in a paraxial region thereof. Thethird lens element 630 is made of plastic material and has theobject-side surface 631 and the image-side surface 632 being bothaspheric.

The fourth lens element 640 with negative refractive power has anobject-side surface 641 being concave in a paraxial region thereof andan image-side surface 642 being concave in a paraxial region thereof.The fourth lens element 640 is made of plastic material and has theobject-side surface 641 and the image-side surface 642 being bothaspheric. The image-side surface 642 of the fourth lens element 640 hasat least one inflection point.

The cover glass 650 is made of glass material and located between thefourth lens element 640 and the image surface 660, and will not affectthe focal length of the optical imaging system. The image sensor 670 isdisposed on or near the image surface 660 of the optical imaging system.

The detailed optical data of the 6th embodiment are shown in Table 11and the aspheric surface data are shown in Table 12 below.

TABLE 11 6th Embodiment f = 0.83 mm, Fno = 2.04, HFOV = 57.0 deg.Surface # Curvature Radius Thickness Material Index Abbe # Focal Length0 Object Plano 400.000 1 Lens 1 −1.330 (ASP) 0.401 Plastic 1.545 56.1−2.09 2 8.779 (ASP) 0.809 3 Ape. Stop Plano 0.023 4 Lens 2 1.747 (ASP)0.525 Plastic 1.534 55.9 −3.19 5 0.772 (ASP) 0.031 6 Lens 3 0.441 (ASP)0.552 Plastic 1.544 56.0 0.51 7 −0.413 (ASP) −0.242 8 Stop Plano 0.272 9Lens 4 −1.328 (ASP) 0.280 Plastic 1.660 20.4 −0.72 10 0.804 (ASP) 0.43011 Cover Glass Plano 0.210 Glass 1.517 64.2 — 12 Plano 0.163 13 ImagePlano — Note: Reference wavelength is 587.6 nm (d-line). An effectiveradius of the stop 601 (Surface 8) is 0.580 mm.

TABLE 12 Aspheric Coefficients Surface # 1 2 4 5 k = −2.5505E+01 0.0000E+00 −6.1127E+01 −1.1001E+01 A4 =  6.2927E−01  2.2752E+00 1.4225E+00 −6.8097E+00 A6 = −8.4846E−01 −7.6931E+00 −4.0685E+01 4.2195E+01 A8 =  9.6605E−01  5.4618E+01  5.4105E+02 −3.7487E+02 A10 =−7.4336E−01 −2.7700E+02 −4.1823E+03  2.0156E+03 A12 =  3.8420E−01 8.4358E+02  1.1595E+04 −5.5003E+03 A14 = −1.2401E−01 −1.2921E+03 — 5.9079E+03 A16 =  1.7331E−02  7.4945E+02 — — Surface # 6 7 9 10 k =−4.7664E+00 −7.6787E+00 −3.5490E−01 −1.5140E+01 A4 = −1.9911E+00−7.6076E−01  2.6451E+00 −1.0077E+00 A6 =  1.6678E+01  1.6589E+01−4.6222E+01 −1.4903E+00 A8 = −1.7581E+02 −2.4839E+02  1.7522E+02 2.7141E+01 A10 =  5.9838E+02  1.3187E+03  9.7687E+01 −8.7941E+01 A12 =−6.2276E+02 −3.1011E+03 −1.9656E+03  1.3151E+02 A14 = —  2.7782E+03 4.1118E+03 −9.6328E+01 A16 = — — −2.6282E+03  2.7925E+01

In the 6th embodiment, the equation of the aspheric surface profiles ofthe aforementioned lens elements is the same as the equation of the 1stembodiment. Also, the definitions of these parameters shown in thefollowing table are the same as those stated in the 1st embodiment withcorresponding values for the 6th embodiment, so an explanation in thisregard will not be provided again.

Moreover, these parameters can be calculated from Table 11 and Table 12as the following values and satisfy the following conditions:

6th Embodiment f [mm] 0.83 f/f3 1.64 Fno 2.04 f/f4 −1.15 HFOV [deg.]57.0 SD/TD 0.54 V4 20.40 TD/T12 3.19 Vmin 20.40 ImgH/f 1.44 CT2/CT3 0.95TL/ImgH 2.88 f/R1 −0.63 TL/f 4.15 (R1 + R2)/(R1 − R2) −0.74 TL [mm] 3.45(R3 − R4)/(R3 + R4) 0.39 f/EPD 2.04 (R5 + R6)/(R5 − R6) 0.03 Yc22/f 0.26f/f2 −0.26 Yi42/f 0.240/0.559/0.709

7th Embodiment

FIG. 13 is a schematic view of an image capturing unit according to the7th embodiment of the present disclosure. FIG. 14 shows, in order fromleft to right, spherical aberration curves, astigmatic field curves anda distortion curve of the image capturing unit according to the 7thembodiment. In FIG. 13, the image capturing unit includes the opticalimaging system (its reference numeral is omitted) of the presentdisclosure and an image sensor 770. The optical imaging system includes,in order from an object side to an image side, a first lens element 710,an aperture stop 700, a second lens element 720, a third lens element730, a stop 701, a fourth lens element 740, a cover glass 750 and animage surface 760. The optical imaging system includes four lenselements (710, 720, 730 and 740) with no additional lens elementdisposed between each of the adjacent four lens elements.

The first lens element 710 with negative refractive power has anobject-side surface 711 being concave in a paraxial region thereof andan image-side surface 712 being concave in a paraxial region thereof.The first lens element 710 is made of plastic material and has theobject-side surface 711 and the image-side surface 712 being bothaspheric. The object-side surface 711 of the first lens element 710 hasat least one convex shape in an off-axis region thereof.

The second lens element 720 with negative refractive power has anobject-side surface 721 being convex in a paraxial region thereof and animage-side surface 722 being concave in a paraxial region thereof. Thesecond lens element 720 is made of plastic material and has theobject-side surface 721 and the image-side surface 722 being bothaspheric. The image-side surface 722 of the second lens element 720 hasat least one critical point in an off-axis region thereof.

The third lens element 730 with positive refractive power has anobject-side surface 731 being convex in a paraxial region thereof and animage-side surface 732 being convex in a paraxial region thereof. Thethird lens element 730 is made of plastic material and has theobject-side surface 731 and the image-side surface 732 being bothaspheric.

The fourth lens element 740 with negative refractive power has anobject-side surface 741 being concave in a paraxial region thereof andan image-side surface 742 being concave in a paraxial region thereof.The fourth lens element 740 is made of plastic material and has theobject-side surface 741 and the image-side surface 742 being bothaspheric. The image-side surface 742 of the fourth lens element 740 hasat least one inflection point.

The cover glass 750 is made of glass material and located between thefourth lens element 740 and the image surface 760, and will not affectthe focal length of the optical imaging system. The image sensor 770 isdisposed on or near the image surface 760 of the optical imaging system.

The detailed optical data of the 7th embodiment are shown in Table 13and the aspheric surface data are shown in Table 14 below.

TABLE 13 7th Embodiment f = 0.82 mm, Fno = 2.04, HFOV = 55.2 deg.Surface # Curvature Radius Thickness Material Index Abbe # Focal Length0 Object Plano 400.000 1 Lens 1 −1.163 (ASP) 0.358 Plastic 1.545 56.1−2.08 2 47.953 (ASP) 0.835 3 Ape. Stop Plano 0.030 4 Lens 2 2.015 (ASP)0.493 Plastic 1.534 55.9 −2.94 5 0.807 (ASP) 0.036 6 Lens 3 0.439 (ASP)0.577 Plastic 1.544 56.0 0.52 7 −0.430 (ASP) −0.236 8 Stop Plano 0.266 9Lens 4 −1.396 (ASP) 0.280 Plastic 1.660 20.4 −0.75 10 0.829 (ASP) 0.43011 Cover Glass Plano 0.210 Glass 1.517 64.2 — 12 Plano 0.174 13 ImagePlano — Note: Reference wavelength is 587.6 nm (d-line). An effectiveradius of the stop 701 (Surface 8) is 0.585 mm.

TABLE 14 Aspheric Coefficients Surface # 1 2 4 5 k = −2.1028E+01 0.0000E+00 −8.6710E+01 −1.5074E+01 A4 =  7.2501E−01  2.5719E+00 1.1992E+00 −6.8321E+00 A6 = −1.0015E+00 −1.0857E+01 −4.1529E+01 4.5307E+01 A8 =  1.1141E+00  8.5118E+01  5.5321E+02 −3.9193E+02 A10 =−8.3010E−01 −4.3663E+02 −4.2411E+03  2.0576E+03 A12 =  4.3301E−01 1.2835E+03  1.1595E+04 −5.5956E+03 A14 = −1.5204E−01 −1.8908E+03 — 6.0583E+03 A16 =  2.4101E−02  1.0662E+03 — — Surface # 6 7 9 10 k =−5.7370E+00 −7.7728E+00  4.5562E−02 −1.5403E+01 A4 = −1.1039E+00 4.6410E−01  3.4431E+00 −6.8369E−01 A6 =  7.8210E+00 −6.2778E+00−6.0195E+01 −4.3037E+00 A8 = −1.0879E+02 −6.0559E+01  2.8808E+02 3.8697E+01 A10 =  3.9022E+02  5.2920E+02 −4.3863E+02 −1.1436E+02 A12 =−4.0842E+02 −1.4298E+03 −5.0010E+02  1.6624E+02 A14 = —  1.3553E+03 2.0406E+03 −1.2082E+02 A16 = — — −1.4991E+03  3.5051E+01

In the 7th embodiment, the equation of the aspheric surface profiles ofthe aforementioned lens elements is the same as the equation of the 1stembodiment. Also, the definitions of these parameters shown in thefollowing table are the same as those stated in the 1st embodiment withcorresponding values for the 7th embodiment, so an explanation in thisregard will not be provided again.

Moreover, these parameters can be calculated from Table 13 and Table 14as the following values and satisfy the following conditions:

7th Embodiment f [mm] 0.82 f/f3 1.58 Fno 2.04 f/f4 −1.09 HFOV [deg.]55.2 SD/TD 0.55 V4 20.40 TD/T12 3.05 Vmin 20.40 ImgH/f 1.40 CT2/CT3 0.85TL/ImgH 3.00 f/R1 −0.71 TL/f 4.20 (R1 + R2)/(R1 − R2) −0.95 TL [mm] 3.45(R3 − R4)/(R3 + R4) 0.43 f/EPD 2.04 (R5 + R6)/(R5 − R6) 0.01 Yc22/f 0.26f/f2 −0.28 Yi42/f 0.255/0.566/0.730

8th Embodiment

FIG. 15 is a schematic view of an image capturing unit according to the8th embodiment of the present disclosure. FIG. 16 shows, in order fromleft to right, spherical aberration curves, astigmatic field curves anda distortion curve of the image capturing unit according to the 8thembodiment. In FIG. 15, the image capturing unit includes the opticalimaging system (its reference numeral is omitted) of the presentdisclosure and an image sensor 870. The optical imaging system includes,in order from an object side to an image side, a first lens element 810,an aperture stop 800, a second lens element 820, a third lens element830, a stop 801, a fourth lens element 840, a cover glass 850 and animage surface 860. The optical imaging system includes four lenselements (810, 820, 830 and 840) with no additional lens elementdisposed between each of the adjacent four lens elements.

The first lens element 810 with negative refractive power has anobject-side surface 811 being concave in a paraxial region thereof andan image-side surface 812 being convex in a paraxial region thereof. Thefirst lens element 810 is made of plastic material and has theobject-side surface 811 and the image-side surface 812 being bothaspheric. The object-side surface 811 of the first lens element 810 hasat least one convex shape in an off-axis region thereof.

The second lens element 820 with negative refractive power has anobject-side surface 821 being convex in a paraxial region thereof and animage-side surface 822 being concave in a paraxial region thereof. Thesecond lens element 820 is made of plastic material and has theobject-side surface 821 and the image-side surface 822 being bothaspheric. The image-side surface 822 of the second lens element 820 hasat least one critical point in an off-axis region thereof.

The third lens element 830 with positive refractive power has anobject-side surface 831 being convex in a paraxial region thereof and animage-side surface 832 being convex in a paraxial region thereof. Thethird lens element 830 is made of plastic material and has theobject-side surface 831 and the image-side surface 832 being bothaspheric.

The fourth lens element 840 with negative refractive power has anobject-side surface 841 being concave in a paraxial region thereof andan image-side surface 842 being concave in a paraxial region thereof.The fourth lens element 840 is made of plastic material and has theobject-side surface 841 and the image-side surface 842 being bothaspheric. The image-side surface 842 of the fourth lens element 840 hasat least one inflection point.

The cover glass 850 is made of glass material and located between thefourth lens element 840 and the image surface 860, and will not affectthe focal length of the optical imaging system. The image sensor 870 isdisposed on or near the image surface 860 of the optical imaging system.

The detailed optical data of the 8th embodiment are shown in Table 15and the aspheric surface data are shown in Table 16 below.

TABLE 15 8th Embodiment f = 0.83 mm, Fno = 2.04, HFOV = 53.5 deg.Surface # Curvature Radius Thickness Material Index Abbe # Focal Length0 Object Plano 400.000 1 Lens 1 −1.033 (ASP) 0.357 Plastic 1.545 56.1−2.35 2 −6.034 (ASP) 0.823 3 Ape. Stop Plano 0.040 4 Lens 2 2.695 (ASP)0.462 Plastic 1.534 55.9 −2.76 5 0.896 (ASP) 0.041 6 Lens 3 0.459 (ASP)0.594 Plastic 1.544 56.0 0.53 7 −0.426 (ASP) −0.235 8 Stop Plano 0.265 9Lens 4 −1.541 (ASP) 0.280 Plastic 1.660 20.4 −0.75 10 0.787 (ASP) 0.43011 Cover Glass Plano 0.210 Glass 1.517 64.2 — 12 Plano 0.176 13 ImagePlano — Note: Reference wavelength is 587.6 nm (d-line). An effectiveradius of the stop 801 (Surface 8) is 0.592 mm.

TABLE 16 Aspheric Coefficients Surface # 1 2 4 5 k = −1.4094E+01 0.0000E+00  1.4774E−01 −1.5544E+01 A4 =  7.7376E−01  2.2282E+00−3.1320E−01 −6.8169E+00 A6 = −1.2160E+00 −5.5493E+00 −3.0935E+01 4.6180E+01 A8 =  1.5463E+00  3.1520E+01  5.0202E+02 −3.9737E+02 A10 =−1.3282E+00 −1.5145E+02 −4.2794E+03  2.0791E+03 A12 =  7.5260E−01 4.4130E+02  1.2330E+04 −5.6964E+03 A14 = −2.5451E−01 −6.3509E+02 — 6.2561E+03 A16 =  3.6887E−02  3.4200E+02 — — Surface # 6 7 9 10 k =−6.0144E+00 −7.3779E+00  7.8691E−02 −1.4774E+01 A4 = −7.8891E−01 6.4039E−03  2.8241E+00 −5.6449E−01 A6 =  4.7488E+00  2.3098E−01−4.7676E+01 −4.3130E+00 A8 = −7.8263E+01 −8.8467E+01  1.9882E+02 3.4608E+01 A10 =  2.9128E+02  5.7270E+02 −1.4509E+02 −9.6861E+01 A12 =−3.0811E+02 −1.4213E+03 −9.7214E+02  1.3429E+02 A14 = —  1.2996E+03 2.3927E+03 −9.2770E+01 A16 = — — −1.5916E+03  2.5314E+01

In the 8th embodiment, the equation of the aspheric surface profiles ofthe aforementioned lens elements is the same as the equation of the 1stembodiment. Also, the definitions of these parameters shown in thefollowing table are the same as those stated in the 1st embodiment withcorresponding values for the 8th embodiment, so an explanation in thisregard will not be provided again.

Moreover, these parameters can be calculated from Table 15 and Table 16as the following values and satisfy the following conditions:

8th Embodiment f [mm] 0.83 f/f3 1.57 Fno 2.04 f/f4 −1.11 HFOV [deg.]53.5 SD/TD 0.55 V4 20.40 TD/T12 3.04 Vmin 20.40 ImgH/f 1.34 CT2/CT3 0.78TL/ImgH 3.07 f/R1 −0.81 TL/f 4.13 (R1 + R2)/(R1 − R2) −1.41 TL [mm] 3.44(R3 − R4)/(R3 + R4) 0.50 f/EPD 2.04 (R5 + R6)/(R5 − R6) 0.04 Yc22/f 0.25f/f2 −0.30 Yi42/f 0.258/0.582/0.726

9th Embodiment

FIG. 17 is a perspective view of an image capturing unit according tothe 9th embodiment of the present disclosure. In this embodiment, animage capturing unit 10 is a camera module including a lens unit 11, adriving device 12, an image sensor 13 and an image stabilizer 14. Thelens unit 11 includes the optical imaging system disclosed in the 1stembodiment, a barrel and a holder member (their reference numerals areomitted) for holding the optical imaging system. The imaging lightconverges in the lens unit 11 of the image capturing unit 10 to generatean image with the driving device 12 utilized for image focusing on theimage sensor 13, and the generated image is then digitally transmittedto other electronic component for further processing.

The driving device 12 can have auto focusing functionality, anddifferent driving configurations can be obtained through the usages ofvoice coil motors (VCM), micro electro-mechanical systems (MEMS),piezoelectric systems, or shape memory alloy materials. The drivingdevice 12 is favorable for obtaining a better imaging position of thelens unit 11, so that a clear image of the imaged object can be capturedby the lens unit 11 with different object distances. The image sensor 13(for example, CCD or CMOS), which can feature high photosensitivity andlow noise, is disposed on the image surface of the optical imagingsystem to provide higher image quality.

The image stabilizer 14, such as an accelerometer, a gyro sensor and aHall Effect sensor, is configured to work with the driving device 12 toprovide optical image stabilization (OIS). The driving device 12 workingwith the image stabilizer 14 is favorable for compensating for pan andtilt of the lens unit 11 to reduce blurring associated with motionduring exposure. In some cases, the compensation can be provided byelectronic image stabilization (EIS) with image processing software,thereby improving image quality while in motion or low-light conditions.

10th Embodiment

FIG. 18 is one perspective view of an electronic device according to the10th embodiment of the present disclosure. FIG. 19 is anotherperspective view of the electronic device in FIG. 18. FIG. 20 is a blockdiagram of the electronic device in FIG. 18.

In this embodiment, an electronic device 20 is a smartphone includingthe image capturing unit 10 disclosed in the 9th embodiment, an imagecapturing unit 10 a, an image capturing unit 10 b, an image capturingunit 10 c, a flash module 21, a focus assist module 22, an image signalprocessor 23, a user interface 24 and an image software processor 25.The image capturing unit 10 c is located on the same side as the userinterface 24, and the image capturing unit 10, the image capturing unit10 a and the image capturing unit 10 b are located on the opposite side.The image capturing unit 10, the image capturing unit 10 a and the imagecapturing unit 10 b all face the same direction, and each of the imagecapturing units 10, 10 a and 10 b has a single focal point. Furthermore,the image capturing unit 10 a, the image capturing unit 10 b and theimage capturing unit 10 c all have a configuration similar to that ofthe image capturing unit 10. In detail, each of the image capturing unit10 a, the image capturing unit 10 b and the image capturing unit 10 cincludes a lens unit, a driving device, an image sensor and an imagestabilizer, and the lens unit includes a lens assembly, a barrel and aholder member for holding the lens assembly.

In this embodiment, the image capturing units 10, 10 a and 10 b havedifferent fields of view (e.g., the image capturing unit 10 a is atelephoto image capturing unit, the image capturing unit 10 is awide-angle image capturing unit and the image capturing unit 10 b is asuper wide-angle image capturing unit), such that the electronic device20 has various magnification ratios so as to meet the requirement ofoptical zoom functionality. In this embodiment, the electronic device 20includes multiple image capturing units 10, 10 a, 10 b and 10 c, but thepresent disclosure is not limited to the number and arrangement of imagecapturing units.

When a user captures images of an object 26, the light rays converge inthe image capturing unit 10, the image capturing unit 10 a or the imagecapturing unit 10 b to generate an image(s), and the flash module 21 isactivated for light supplement. The focus assist module 22 detects theobject distance of the imaged object 26 to achieve fast auto focusing.The image signal processor 23 is configured to optimize the capturedimage to improve image quality. The light beam emitted from the focusassist module 22 can be either conventional infrared or laser. Inaddition, the electronic device 20 can capture images of the object 26via the image capturing unit 10 c. The user interface 24 can be a touchscreen or a physical button. The user is able to interact with the userinterface 24 and the image software processor 25 having multiplefunctions to capture images and complete image processing. The imageprocessed by the image software processor 25 can be displayed on theuser interface 24.

The smartphone in this embodiment is only exemplary for showing theimage capturing unit 10 of the present disclosure installed in anelectronic device, and the present disclosure is not limited thereto.The image capturing unit 10 can be optionally applied to optical systemswith a movable focus. Furthermore, the optical imaging system of theimage capturing unit 10 features good capability in aberrationcorrections and high image quality, and can be applied to 3D(three-dimensional) image capturing applications, in products such asdigital cameras, mobile devices, digital tablets, smart televisions,network surveillance devices, dashboard cameras, vehicle backup cameras,multi-camera devices, image recognition systems, motion sensing inputdevices, wearable devices and other electronic imaging devices.

The foregoing description, for the purpose of explanation, has beendescribed with reference to specific embodiments. It is to be noted thatTABLES 1-16 show different data of the different embodiments; however,the data of the different embodiments are obtained from experiments. Theembodiments were chosen and described in order to best explain theprinciples of the disclosure and its practical applications, to therebyenable others skilled in the art to best utilize the disclosure andvarious embodiments with various modifications as are suited to theparticular use contemplated. The embodiments depicted above and theappended drawings are exemplary and are not intended to be exhaustive orto limit the scope of the present disclosure to the precise formsdisclosed. Many modifications and variations are possible in view of theabove teachings.

What is claimed is:
 1. An optical imaging system comprising four lenselements, the four lens elements being, in order from an object side toan image side, a first lens element, a second lens element, a third lenselement and a fourth lens element; each of the four lens elements havingan object-side surface facing toward the object side and an image-sidesurface facing toward the image side; wherein the object-side surface ofthe first lens element is concave in a paraxial region thereof and hasat least one convex shape in an off-axis region thereof, the object-sidesurface of the first lens element is aspheric, the image-side surface ofthe fourth lens element is concave in a paraxial region thereof, and theoptical imaging system has a total of four lens elements; wherein anaxial distance between the object-side surface of the first lens elementand an image surface is TL, a focal length of the optical imaging systemis f, a focal length of the second lens element is f2, an axial distancebetween the first lens element and the second lens element is T12, anaxial distance between the second lens element and the third lenselement is T23, an axial distance between the third lens element and thefourth lens element is T34, a maximum image height of the opticalimaging system is ImgH, and the following conditions are satisfied:3.0<TL/f<6.0; T23<T12; T34<T12; −1.0<f/f2<0.25; and 2.0<TL/ImgH<3.50. 2.The optical imaging system of claim 1, wherein the first lens elementhas negative refractive power, the third lens element has positiverefractive power, and the fourth lens element has negative refractivepower.
 3. The optical imaging system of claim 1, wherein the object-sidesurface of the third lens element is convex in a paraxial regionthereof, the image-side surface of the third lens element is convex in aparaxial region thereof, a central thickness of the first lens elementis CT1, a central thickness of the second lens element is CT2, a centralthickness of the third lens element is CT3, a central thickness of thefourth lens element is CT4, and the following conditions are satisfied:CT1<CT3; CT2<CT3; and CT4<CT3.
 4. The optical imaging system of claim 1,wherein an Abbe number of the fourth lens element is V4, and thefollowing condition is satisfied: 10.0<V4<23.0.
 5. The optical imagingsystem of claim 1, further comprising an aperture stop, wherein theaperture stop is disposed between the first lens element and the secondlens element.
 6. The optical imaging system of claim 1, wherein thefocal length of the optical imaging system is f, a curvature radius ofthe object-side surface of the first lens element is R1, and thefollowing condition is satisfied: −2.0<f/R1<−0.50.
 7. The opticalimaging system of claim 1, wherein the maximum image height of theoptical imaging system is ImgH, the focal length of the optical imagingsystem is f, an entrance pupil diameter of the optical imaging system isEPD, and the following conditions are satisfied: 1.20<ImgH/f<3.0; and1.0<f/EPD<2.25.
 8. An optical imaging system comprising four lenselements, the four lens elements being, in order from an object side toan image side, a first lens element, a second lens element, a third lenselement and a fourth lens element; each of the four lens elements havingan object-side surface facing toward the object side and an image-sidesurface facing toward the image side; wherein the object-side surface ofthe first lens element is concave in a paraxial region thereof and hasat least one convex shape in an off-axis region thereof, the object-sidesurface of the first lens element is aspheric, the object-side surfaceof the third lens element is convex in a paraxial region thereof, theimage-side surface of the fourth lens element is concave in a paraxialregion thereof, the image-side surface of the fourth lens element has atleast one inflection point, and the optical imaging system has a totalof four lens elements; wherein the optical imaging system furthercomprises an aperture stop, an axial distance between the object-sidesurface of the first lens element and an image surface is TL, a focallength of the optical imaging system is f, an axial distance between thefirst lens element and the second lens element is T12, an axial distancebetween the second lens element and the third lens element is T23, anaxial distance between the third lens element and the fourth lenselement is T34, an axial distance between the aperture stop and theimage-side surface of the fourth lens element is SD, an axial distancebetween the object-side surface of the first lens element and theimage-side surface of the fourth lens element is TD, and the followingconditions are satisfied: 3.0<TL/f<6.0′ T23<T12; T34<T12;0.34<SD/TD<1.20; and 0.50 mm<IL<4.0 mm.
 9. The optical imaging system ofclaim 8, wherein the object-side surface of the fourth lens element isconcave in a paraxial region thereof.
 10. The optical imaging system ofclaim 8, wherein the focal length of the optical imaging system is f, acurvature radius of the object-side surface of the first lens element isR1, and the following condition is satisfied: −2.0<f/R1<−0.50.
 11. Theoptical imaging system of claim 8, wherein the axial distance betweenthe object-side surface of the first lens element and the image-sidesurface of the fourth lens element is TD, the axial distance between thefirst lens element and the second lens element is T12, and the followingcondition is satisfied: 1.20<TD/T12<3.50.
 12. The optical imaging systemof claim 8, wherein a curvature radius of the object-side surface of thesecond lens element is R3, a curvature radius of the image-side surfaceof the second lens element is R4, and the following condition issatisfied: −0.45<(R3−R4)/(R3+R4)<1.45.
 13. The optical imaging system ofclaim 8, wherein the focal length of the optical imaging system is f, afocal length of the third lens element is f3, a minimum value among Abbenumbers of all lens elements of the optical imaging system is Vmin, andthe following conditions are satisfied: 1.0<f/f3<3.50; and Vmin<22.5.14. An image capturing unit, comprising: the optical imaging system ofclaim 8; and an image sensor disposed on the image surface of theoptical imaging system.
 15. An electronic device, comprising: the imagecapturing unit of claim
 14. 16. An optical imaging system comprisingfour lens elements, the four lens elements being, in order from anobject side to an image side, a first lens element, a second lenselement, a third lens element and a fourth lens element; each of thefour lens elements having an object-side surface facing toward theobject side and an image-side surface facing toward the image side;wherein the object-side surface of the first lens element is concave ina paraxial region thereof, the image-side surface of the second lenselement is concave in a paraxial region thereof, the image-side surfaceof the fourth lens element is concave in a paraxial region thereof, andthe optical imaging system has a total of four lens elements; whereinthe optical imaging system further comprises an aperture stop, an axialdistance between the object-side surface of the first lens element andan image surface is TL, a focal length of the optical imaging system isf, a focal length of the fourth lens element is f4, an axial distancebetween the aperture stop and the image-side surface of the fourth lenselement is SD, an axial distance between the object-side surface of thefirst lens element and the image-side surface of the fourth lens elementis TD, a curvature radius of the object-side surface of the first lenselement is R1, a curvature radius of the image-side surface of the firstlens element is R2, an Abbe number of the fourth lens element is V4, andthe following conditions are satisfied: 3.0<TL/f<10.0; 0.34<SD/TD<1.20;(R1+R2)/(R1−R2)<0.90; −3.0<f/f4<−0.55; and 10.0<V4<23.0.
 17. The opticalimaging system of claim 16, wherein the object-side surface of the firstlens element has at least one convex shape in an off-axis regionthereof, a central thickness of the second lens element is CT2, acentral thickness of the third lens element is CT3, and the followingcondition is satisfied: 0.10<CT2/CT3<1.50.
 18. The optical imagingsystem of claim 16, wherein the curvature radius of the object-sidesurface of the first lens element is R1, the curvature radius of theimage-side surface of the first lens element is R2, and the followingcondition is satisfied: −10.0<(R1+R2)/(R1−R2)<0.50.
 19. The opticalimaging system of claim 16, wherein a curvature radius of theobject-side surface of the third lens element is R5, a curvature radiusof the image-side surface of the third lens element is R6, and thefollowing condition is satisfied: −0.80<(R5+R6)/(R5−R6)<0.80.
 20. Theoptical imaging system of claim 16, wherein a vertical distance betweena critical point on the image-side surface of the second lens elementand an optical axis is Yc22, the focal length of the optical imagingsystem is f, and the following condition is satisfied: 0.05<Yc22/f<0.70.21. An optical imaging system comprising four lens elements, the fourlens elements being, in order from an object side to an image side, afirst lens element, a second lens element, a third lens element and afourth lens element; each of the four lens elements having anobject-side surface facing toward the object side and an image-sidesurface facing toward the image side; wherein the object-side surface ofthe first lens element is concave in a paraxial region thereof and hasat least one convex shape in an off-axis region thereof, the object-sidesurface of the first lens element is aspheric, the object-side surfaceof the third lens element is convex in a paraxial region thereof, andthe optical imaging system has a total of four lens elements; wherein anaxial distance between the object-side surface of the first lens elementand an image surface is TL, a focal length of the optical imaging systemis f, a focal length of the second lens element is f2, a minimum valueamong Abbe numbers of all lens elements of the optical imaging system isVmin, and the following conditions are satisfied: 3.50<TL/f<5.0;Vmin<22.5; and −3.0<f/f2<0.40; wherein a vertical distance between aninflection point on the image-side surface of the fourth lens elementand an optical axis is Yi42, and the image-side surface of the fourthlens element has at least one inflection point satisfying the followingcondition: 0.10<Yi42/f<1.20.
 22. The optical imaging system of claim 21,wherein the first lens element has negative refractive power, the thirdlens element has positive refractive power, and the fourth lens elementhas negative refractive power.
 23. The optical imaging system of claim21, wherein an axial distance between the object-side surface of thefirst lens element and the image-side surface of the fourth lens elementis TD, an axial distance between the first lens element and the secondlens element is T12, a central thickness of the first lens element isCT1, a central thickness of the second lens element is CT2, a centralthickness of the third lens element is CT3, a central thickness of thefourth lens element is CT4, and the following conditions are satisfied:1.20<TD/T12<3.50; CT1<CT3; CT2<CT3; and CT4<CT3.
 24. The optical imagingsystem of claim 21, wherein the minimum value among Abbe numbers of alllens elements of the optical imaging system is Vmin, and the followingcondition is satisfied: 10.0<Vmin<20.5.